Similar meaning:
* Transient
* Ephemeral
* Momentary
* Passing
* Short-lived
* Fugitive
* Vanishing
* Transitory
* Brief
* Elusive
More descriptive:
* Whizzing by
* Flitting
* Darting
* Rushing
* Speeding
* Flashing
The best word to use will depend on the specific context and the nuance you want to convey.